Sorus (?), n.; pl. Sori (#). [NL., fr. Gr. &unr_; a heap.] 1. (Bot.) One of the fruit dots, or small clusters of sporangia, on the back of the fronds of ferns.
[1913 Webster]

2. (a) In parasitic fungi, any mass of spores bursting through the epidermis of a host plant. (b) In lichens, a heap of soredia on the thallus.
[Webster 1913 Suppl.]